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CAIE A-Level Biology AS 2.3 Proteins Questions

Practise CAIE AS Biology 2.3 by explaining how amino-acid sequence, protein structure and molecular interactions determine function.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • Describe amino-acid structure and R groups; explain peptide-bond formation by condensation and hydrolysis.
  • Distinguish primary, secondary, tertiary and quaternary protein structures and their stabilising interactions.
  • Relate hydrophobic, hydrogen, ionic and disulfide bonds to protein shape; peptide bonds link amino acids.
  • Contrast generally soluble, physiological globular proteins with generally insoluble, structural fibrous proteins.
  • Describe haemoglobin's two α and two β chains and haem; explain Fe2+ oxygen binding and transport.
  • Relate collagen's glycine-rich triple helix, hydrogen bonds and cross-links to tensile strength in fibres.

Covered syllabus points

2.3.1—Amino acids and peptide bonds2.3.2—Protein structure levels2.3.3—Interactions holding protein shape2.3.4—Globular proteins2.3.5—Fibrous proteins2.3.6—Haemoglobin quaternary structure2.3.7—Haemoglobin function2.3.8—Collagen structure2.3.9—Collagen structure and function

Question 1

[Maximum number: 1]

Which statements about peptide bond formation are correct?
1 The bond formation occurs between a carbon of one amino acid and a nitrogen of the next amino acid after the amino acids detach from tRNA.

2 The bond formation occurs at the ribosome while the amino acids are still attached to tRNA, and is a hydrolysis reaction.

3 The bond formation is important for growth of an organism and when the bond forms, a water molecule is removed.

A

1 and 3

B

2 and 3

C

2 only

D

3 only

Question 2

[Maximum number: 1]

Which fact about the quaternary structure of proteins is correct?

A

consists of four polypeptides

B

depends on the presence of metal ions

C

depends on the primary structure of the polypeptides

D

is made of α\alpha and β\beta polypeptides

Question 3

[Maximum number: 1]

Which row correctly identifies the weak and strong bonds in the tertiary and quaternary structure of a typical protein?

disulfide

hydrogen

hydrophobic

ionic

strong

strong

weak

weak

strong

weak

weak

weak

weak

weak

strong

strong

weak

weak

weak

strong

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